How do I select an object in the 3D viewport?
That circle/crosshair is the 3D cursor.
To select you need to Right click instead of Left click.
You can change this behavior in File &gt; User Preferences (CtrlAltU) &gt; Input:

Open the User Preferences:



Go to the Input tab. The select left/right options are under Mouse:



If you want to save these settings as the default for the next time you open blender, click  Save User Settings in the Header (at the bottom of the window):


This is one of the most controversial parts of blenders UI.
For some further information you might want to check out:

&quot;Fixing Blender – Part 1: Why It’s Broken&quot; by Andrew Price

This video by Sebastian König explaining some advantages to using RMB to select

&quot;Fixing Blender – Part 2&quot; by Andrew Price

This 3 hour discussion about Blender's interface

&quot;New Blender UI Proposal&quot; by Andrew Price

The manual on object selection